The Fe/N/C catalysts have emerged recently as a representative class of non-Pt catalysts for oxygen electrocatalytic reduction, which could have a competitive catalytic performance to Pt. However, the nature of the catalyst remains elusive, especially on the active site structure and the electrocatalytic kinetics. Here we examine two kinds of Fe/N active sites for Fe/N/C catalysts, namely, the four-coordinated FeN4 and the five-coordinated Fe(CN)N4 centers embedded in graphene layers. By using large-scale first principles calculations with a periodic continuum solvation model based on the Modified-Poisson-Boltzmann equation (CM-MPB), we identified the four (4e) and two electron (2e) oxygen reduction pathways under acidic conditions. We find that both 4e and 2e pathways involves the formation of an OOH intermediate, which breaks its O-OH bond in the 4e pathway but is reduced to H2O2 in the 2e pathway. We show that at 0.8 V vs. SHE, the 4e pathway is preferred at both FeN4 and Fe(CN)N4 centers, but the 2e pathway is kinetically also likely on the Fe(CN)N4 center. The O-OH bond breaking of OOH is the key kinetic step, which has a similar free energy barrier to the OH reduction on the FeN4 center, and is the rate-determining step on the Fe(CN)N4 center. Due to the high adsorption energy of Fe towards the fifth ligand, such as OH and CN, we expect that the active site of the real Fe/N/C catalyst is the five coordinated Fe center. We found that the barrier of the O-OH bond breaking step is not sensitive to potential and a Tafel slope of 60 mV is predicted for the ORR on the Fe(CN)N4 center, which is consistent with experimental observation.

DNA base oxidation is considered to be a key event associated with disease initiation and progression in humans. Peroxyl radicals (ROO. ) are important oxidants found in cells whose ability to react with the DNA bases has not been characterized extensively. In this paper, the products resulting from ROO. oxidation of the DNA bases are determined by gas chromatography/MS in comparison with authentic standards. ROO. radicals oxidize adenine and guanine to their 8-hydroxy derivatives, which are considered biomarkers of hydroxyl radical (HO.) oxidations in cells. ROO. radicals also oxidize adenine to its hydroxylamine, a previously unidentified product. ROO. radicals oxidize cytosine and thymine to the monohydroxy and dihydroxy derivatives that are formed by oxidative damage in cells. Identical ROO. oxidation profiles are observed for each base when exposed as deoxyribonucleosides, monohomopolymers and base-paired dihomopolymers. These results have significance for the development, utilization and interpretation of DNA base-derived biomarkers of oxidative damage associated with disease initiation and propagation, and support the idea that the mutagenic potential of N-oxidized bases, when generated in cellular DNA, will require careful evaluation. Adenine hydroxylamine is proposed as a specific molecular probe for the activity of ROO. in cellular systems.

We report herein a visible light induced generation of a carbanion via double-SET and its application in cyclopropanation of alkenes. This new synthetic approach to form cyclopropane derivatives was conducted under mild conditions, using sunlight in open air, showing the features such as environmental benignness and an easy to handle procedure.

A terminal alkyne-assisted protocol for the one-pot formation of a diverse range of arylamidines from a novel cascade reaction of in situ generated nitrile oxides, sulfonyl azides, terminal alkynes, and water by [3 + 2] cycloaddition and ring opening sequence was developed. The use of aryl oxime chlorides as the carbon source of the amidine group and the addition of water proved to be critical for the reaction. Moreover, terminal alkynes, which can lead to high yields of products by employing a less amount, may play a catalytic role in the reaction. A broader range of substrates was investigated.

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Benzo[f]pyrido[1,2-a]indole-6,11-diones have been synthesized in high yields by copper(II)-catalyzed three-component reactions of acyl bromide, 1,4-naphthoquinone, and pyridine (or isoquinoline) via sp(2)-C-H difunctionalization of naphthoquinone followed by intramolecular cyclization and oxidative aromatization. In an attempt to expand the reaction scope and to help clarify the reaction mechanism, 1,3-dicarbonyl compounds are used in place of acyl bromides to take part in this reaction, and the benzo[f]pyrido[1,2-a]indole-6,11-diones derivatives are also obtained in excellent yields.

In situ synthesis of a cost-effective g-C3N4/Fe2O3 hybrid with enhanced photocatalytic activity for the degradation of organic pollutants based on the direct Z-scheme mechanism.

The C-S cross-coupling of aryl halides with alkyl thiols catalyzed by in-situ generated Ni (II) N-heterocyclic carbene (NHC) complexes is investigated. Good to excellent yields can be obtained for a variety of aryl halides when using 5 mol% of the Ni (II)-NHC catalyst and 1.5 eq. of KO t Bu. Both the electronic and steric effects of the NHC ligands on the catalytic performance of Ni (II)-NHC, as well as the electronic effects of aryl halides on coupling reactivity are examined. The mechanism for Ni (II)-NHC catalyzed coupling reactions is also discussed.